Population dynamics of rice rats (a Hantavirus reservoir) in southern Chile: feedback structure and non‐linear effects of climatic oscillations

Abstract

We studied a fluctuating population of the long‐tail rice rat (Oligoryzomys longicaudatus), the main Hantavirus vector in southern Chile, and spanning 19 years of monitoring. We determined that a first‐order feedback structure and non‐linear effects of Antarctic Oscillation Index (AAOI) and Southern Oscillation Index (SOI) explain 96% of the variation in annual per capita population growth rates. One important result of this study is that first‐order feedback structure captures the essential features of population dynamics of long‐tailed rice rats. This regulatory structure suggests that rice rats are limited by food, space or predators and regulated by intra‐specific competition. The first‐order dynamics observed in long‐tailed rice rats strongly suggests that Hantavirus have no harmful effects on survival or reproductive processes. Besides the non‐linear climatic signature in population dynamics, the periodic event of bamboo‐flowering and mast seeding strongly influence rice rats population growth rates. Because of this, bamboo flowering may be used as a signal for forecasting long‐tail rice rats outbreaks and for implementing information and health policies to avoid human‐rodent contacts in specific areas. The observed effects of the two large‐scale climatic indexes that influence climatic variability along southern Pacific Ocean, the AAOI and the SOI, emphasizes the role of considering non‐linear feedback structures and climatic forces for understanding small rodent population dynamics. Because long‐tailed rice rats represent the major Hantavirus reservoir in southern Chile and Argentina, we need to gain an in‐depth understanding of the structure and functioning of these small rodent populations in face of the potential consequences of global change and climatic fluctuations.